1. Field of the Invention
The present invention relates to a coding apparatus and method, a decoding apparatus and method, and a record medium. More particularly, the present invention relates to a coding apparatus and method, a decoding apparatus and method, and a record medium, in which an image can be prevented from being displayed in a display state which is against the intentions of the producer.
2. Description of the Related Art
FIG. 10 shows an example of the construction of a conventional coding apparatus for coding image signals. In this example, an image generated in an image generating apparatus 1 is supplied to a video coder 11 of a coding apparatus 2 in accordance with a predetermined sequence. The image generating apparatus 1 further generates a frame number and outputs it to the video coder 11. Furthermore, the image generating apparatus 1 time information for the generated image and supplies it to a multiplexer 12 of the coding apparatus 2. The video coder 11 codes the input image and outputs the coded data (video codes) to the multiplexer 12. The multiplexer 12 multiplexes the video codes input from the video coder 11 onto the time information input from the image generating apparatus 1, and outputs it as a bitstream.
Next, the operation of the coding apparatus will be described. The video coder 11 codes the image input from the image generating apparatus 1 together with the frame number by an MPEG (Moving Picture Experts Group) method. Then, the video coder 11 outputs the video codes obtained as a result of the coding to the multiplexer 12. The multiplexer 12 multiplexes the time information output from the image generating apparatus 1 onto the video codes output from the video coder 11, and outputs it as a bitstream.
FIG. 11 shows an example of the construction of a decoding apparatus for decoding a bitstream which is coded by the coding apparatus and which is output therefrom in this way. In this example, a bitstream is input to a demultiplexer 31 of a decoding apparatus 21. The demultiplexer 31 demultiplexes (isolates) video codes from the input bitstream. The video codes output from the demultiplexer 31 are input to a video decoder 32. The video decoder 32 decodes the input video codes and outputs an image to a horizontal filter 33. The horizontal filter 33 performs an operation of enlarging or reducing the horizontal length of the input image signals, and outputs it to a vertical filter 34. The vertical filter 34 performs an operation of enlarging or reducing the vertical length of the input signals, and outputs it to a monitor 22 and a monitor 23.
The time information isolated by the demultiplexer 31, and the frame number which is decoded and output by the video decoder 32 are not particularly used in this example. Therefore, a description thereof is omitted.
A control signal is input to a controller 35 from an apparatus (not shown). The controller 35, in response to this control signal, controls the horizontal filter 33 and the vertical filter 34.
In the image decoding apparatus shown in FIG. 11, an encoder for converting the image signals output from the video decoder 32 into signals of an NTSC (National Television System Committee) system is omitted.
Next, the operation of the image decoding apparatus will be described below. The demultiplexer 31 isolates video codes from the input bitstream and outputs them to the video decoder 32. The video decoder 32 isolates image signals from the input video codes and outputs them to the horizontal filter 33.
The image signals obtained as a result of decoding by the video decoder 32, as shown in FIG. 12(A), are made to be an image for the monitor 23 having an aspect ratio of 16:9. That is, for this image, an image to be displayed on the monitor 23 having an aspect ratio of 16:9 is made to be an image having an aspect ratio of 4:3 by compressing (thereby forming into an oblong image) the length of the image in a horizontal direction, thus forming an oblong image having an aspect ratio of 4:3.
In a case in which the user sees this decoded image on the monitor 23 having an aspect ratio of 16:9, the user inputs an external control signal to the controller 35, causing the horizontal filter 33 to be turned off, as well as the vertical filter 34. As a result, the oblong image, shown in FIG. 12(A), which is output from the video decoder 32, is output unchanged from the horizontal filter 33 which is turned off, as shown in FIG. 12(C). At this time, since the vertical filter 34 is also turned off, the vertical filter 34, as shown in FIG. 12(E), outputs this image as is on the monitor 23. Since the monitor 23 has an aspect ratio of 16:9, an image (an oblong image) whose length is compressed in the horizontal direction is expanded in the horizontal direction. As a result, a normal image (an image whose ratio of length to width is the same and which has no lost portions), shown in FIG. 12(I), is displayed on the monitor 23. As a result, it is possible to enjoy a dynamic image having a wide screen.
Incidentally, in a case in which the user does not have a monitor 23 having an aspect ratio of 16:9, but has only a monitor 22 having an aspect ratio of 4:3, the user is able to select and instruct any one of the modes such as a squeezed mode, a letter box mode, and an edge cropped mode by inputting an external control signal to the controller 35.
The controller 35, when the squeezed mode is instructed, turns off both the horizontal filter 33 and the vertical filter 34. As a result, when the image shown in FIG. 12(E) is input to the vertical filter 34, the vertical filter 34 outputs the image as is onto the monitor 22 without performing any special process. As a result, an oblong image shown in FIG. 12(H) is displayed as is on the monitor 22 having an aspect ratio of 4:3.
On the other hand, in a case in which a letter box mode is instructed, the controller 35 turns off the horizontal filter 33 and turns on the vertical filter 34. When an oblong image shown in FIG. 12(C) is input via the horizontal filter 33, the vertical filter 34 performs an operation of compressing the length of the image in the vertical direction. As a result of this operation, an image is obtained whose ratio of length to width is the same. However, since regions where there is substantially no image, are formed in the upper and lower portions of the screen having an aspect ratio of 4:3, a black-level image is inserted into those regions, and thus an image such as that shown in FIG. 12(D) is formed. When this image is output from the vertical filter 34 and is displayed on a monitor 22 having an aspect ratio of 4:3, as shown in FIG. 12(G), an image in which no-signal regions are formed in the upper and lower portions of the screen is displayed as a normal image whose ratio of length to width is 1:1.
Further, when an edge cropped mode is instructed, the controller 35 turns on the horizontal filter 33 and turns off the vertical filter 34. When an oblong image shown in FIG. 12(A) is input from the video decoder 32, the horizontal filter 33 removes the image near the left and right end portions of this image. As a result, an image shown in FIG. 12(B) is obtained. When this image is displayed on the monitor 22 having an aspect ratio of 4:3 via the vertical filter 34, an image such as that shown in FIG. 12(F) is displayed on the monitor 22. This image is an image whose ratio of length to width is 1:1; however, a part of the image near the left and right end portions of this image is lost.
As described above, the edge cropped mode from among the above-described modes is a mode in which a part of an image is cut and displayed in order to adjust it to a monitor having an aspect ratio of 4:3. For this reason, since in this mode an image different from the intentions of the producer of the image is displayed, there is a risk in that a problem concerning copyright might occur.
In order to avoid this problem, by making the producer of the image specify by a portion of the image to be cut in the edge cropped mode, permission for coding the image may thus be obtained. However, for example, when a title or a person's name is displayed on the entire screen, it is often not possible to cut any portion. In such a case, since a part of the title or the person's name is cut when a display is made in the above-described edge cropped mode, as a result, a situation may arise in which permission for coding the image (e.g., a movie) and recording it on a record (recording, recordable or recorded) medium, and for transmitting the image cannot be obtained from the producer of the image.